def get(self, path, watcher=None):
"""
gets the data associated with a node synchronously.
PARAMETERS:
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
(subsequent parameters are optional)
watcher: if not None, a watch will be set at the server to notify
the client if the node changes.
RETURNS:
the (data, stat) tuple associated with the node
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.aget(self._zhandle, path, watcher,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as data_completion
handle, rc, data, stat = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return (data, stat)
self._raise_exception(rc)
def set_acl(self, path, version, acl):
"""sets the acl associated with a node synchronously.
PARAMETERS:
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
version: the expected version of the path.
acl: the acl to be set on the path.
RETURNS:
OK operation completed successfully
EXCEPTIONS:
NONODE the node does not exist.
NOAUTH the client does not have permission.
INVALIDACL invalid ACL specified
BADVERSION expected version does not match actual version.
BADARGUMENTS - invalid input parameters
INVALIDSTATE - zhandle state is either SESSION_EXPIRED_STATE
or AUTH_FAILED_STATE
MARSHALLINGERROR - failed to marshall a request; possibly, out
of memory
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.aset_acl(
self._zhandle, path, version, acl,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as void_completion
handle, rc = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return rc
self._raise_exception(rc)
def exists(self, path, watch=None):
"""checks the existence of a node in zookeeper.
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
(Subsequent parameters are optional)
watch: if not None, a watch will be set at the server to notify the
client if the node changes. The watch will be set even if the node does not
exist. This allows clients to watch for nodes to appear.
Return: stat if the node exists
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.aexists(
self._zhandle, path, watch,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as stat_completion
handle, rc, stat = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return stat
self._raise_exception(rc)
def create(self, path, value, acl=None, flags=0):
"""
create a node synchronously.
This method will create a node in ZooKeeper. A node can only be created if
it does not already exists. The Create Flags affect the creation of nodes.
If the EPHEMERAL flag is set, the node will automatically get removed if the
client session goes away. If the SEQUENCE flag is set, a unique
monotonically increasing sequence number is appended to the path name.
PARAMETERS:
path: The name of the node. Expressed as a file name with slashes
separating ancestors of the node.
value: The data to be stored in the node.
acl: The initial ACL of the node. If None, the ACL of the parent will be
used.
flags: this parameter can be set to 0 for normal create or an OR
of the Create Flags
The real path that is created (this might be different than the
path to create because of the SEQUENCE flag.
the maximum length of real path you would want.
RETURNS:
The actual znode path that was created (may be different from path due
to use of SEQUENTIAL flag).
EXCEPTIONS:
NONODE the parent node does not exist.
NODEEXISTS the node already exists
NOAUTH the client does not have permission.
NOCHILDRENFOREPHEMERALS cannot create children of ephemeral nodes.
BADARGUMENTS - invalid input parameters
INVALIDSTATE - zhandle state is either SESSION_EXPIRED_STATE or
AUTH_FAILED_STATE
MARSHALLINGERROR - failed to marshall a request; possibly, out of
memory
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.acreate(
self._zhandle, path, value, acl, flags,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as string_completion
handle, rc, real_path = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return real_path
self._raise_exception(rc)
def __init__(self,
host,
timeout=10,
recv_timeout=10000,
ident=(-1, ""),
zklog_fd=None):
"""
This method creates a new handle and a zookeeper session that corresponds
to that handle. Session establishment is asynchronous, meaning that the
session should not be considered established until (and unless) an
event of state CONNECTED_STATE is received.
PARAMETERS:
host: comma separated host:port pairs, each corresponding to a zk
server. e.g. '127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002'
(subsequent parameters are optional)
fn: the global watcher callback function. When notifications are
triggered this function will be invoked.
recv_timeout:
ident = (clientid, passwd)
clientid the id of a previously established session that this
client will be reconnecting to. Clients can access the session id of an
established, valid,
connection by calling zoo_client_id. If
the specified clientid has expired, or if the clientid is invalid for
any reason, the returned zhandle_t will be invalid -- the zhandle_t
state will indicate the reason for failure (typically
EXPIRED_SESSION_STATE).
zklog_fd is the file descriptor to redirect zookeeper logs.
By default, it redirects to /dev/null
"""
self._zhandle = None
pc = utils.PipeCondition()
def init_watcher(handle, event_type, stat, path):
#called when init is successful
pc.notify()
if zklog_fd is None:
zklog_fd = open("/dev/null")
zookeeper.set_log_stream(zklog_fd)
self._zhandle = zookeeper.init(host, init_watcher, recv_timeout, ident)
pc.wait(timeout)
def dequeue(self, timeout=None):
'''
concurrent dequeue
blocking for 'timeout' seconds;
if timeout is None, block indefinitely (by default)
if timeout is 0, equivalent to non-blocking
'''
def watcher(pc, handle, event, state, path):
pc.notify()
while True:
pc = utils.PipeCondition()
children = sorted(
self._session.get_children(self.basepath,
functools.partial(watcher, pc)))
for child in children:
data = self._get_and_delete(self.basepath + "/" + child)
if data is not None:
return data
pc.wait(timeout)
def sync(self, path):
"""
Flush leader channel.
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
Returns OK on success.
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper. async (self._zhandle, path,
functools.partial(generic_completion, pc,
results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as void_completion
handle, rc = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return rc
self._raise_exception(rc)
def delete(self, path, version=-1):
"""
delete a node in zookeeper synchronously.
PARAMETERS:
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
(Subsequent parameters are optional)
version: the expected version of the node. The function will fail if the
actual version of the node does not match the expected version.
If -1 (the default) is used the version check will not take place.
RETURNS:
OK operation completed successfully
One of the following exceptions is returned when an error occurs.
NONODE the node does not exist.
NOAUTH the client does not have permission.
BADVERSION expected version does not match actual version.
NOTEMPTY children are present; node cannot be deleted.
BADARGUMENTS - invalid input parameters
INVALIDSTATE - zhandle state is either SESSION_EXPIRED_STATE or
AUTH_FAILED_STATE
MARSHALLINGERROR - failed to marshal a request; possibly, out of
memory
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.adelete(
self._zhandle, path, version,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as void_completion
handle, rc = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return rc
self._raise_exception(rc)
def set2(self, path, data, version=-1):
"""
sets the data associated with a node.
PARAMETERS:
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
data: the buffer holding data to be written to the node.
(subsequent parameters are optional)
version: the expected version of the node. The function will fail if
the actual version of the node does not match the expected version.
If -1 is used the version check will not take place.
RETURNS:
the new stat of the node.
EXCEPTIONS:
NONODE the node does not exist.
NOAUTH the client does not have permission.
BADVERSION expected version does not match actual version.
BADARGUMENTS - invalid input parameters
INVALIDSTATE - zhandle state is either SESSION_EXPIRED_STATE or
AUTH_FAILED_STATE
MARSHALLINGERROR - failed to marshall a request; possibly, out of
memory
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.aset(self._zhandle, path, data, version,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as stat_completion
handle, rc, stat = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return stat
self._raise_exception(rc)
def get_acl(self, path):
"""
Gets the acl associated with a node.
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
Return:
(acl, stat)
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.aget_acl(
self._zhandle, path,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as acl_completion
handle, rc, acl, stat = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return (acl, stat)
self._raise_exception(rc)
def get_children(self, path, watcher=None):
"""
lists the children of a node synchronously.
PARAMETERS:
path: the name of the node. Expressed as a file name with slashes
separating ancestors of the node.
(subsequent parameters are optional)
watcher: if non-null, a watch will be set at the server to notify
the client if the node changes.
RETURNS:
A list of znode names
EXCEPTIONS:
NONODE the node does not exist.
NOAUTH the client does not have permission.
BADARGUMENTS - invalid input parameters
INVALIDSTATE - zhandle state is either SESSION_EXPIRED_STATE
or AUTH_FAILED_STATE
MARSHALLINGERROR - failed to marshall a request; possibly, out
of memory
"""
results = []
pc = utils.PipeCondition()
ok = zookeeper.aget_children(
self._zhandle, path, watcher,
functools.partial(generic_completion, pc, results))
assert ok == zookeeper.OK
pc.wait()
#unpack result as strings_completion
handle, rc, children = results
assert handle == self._zhandle
if rc == zookeeper.OK:
return children
self._raise_exception(rc)